Blown out TIFF image after merge in QGIS?

Question

I'm attempting to merge four GeoTIFF images in QGIS for the first time and am getting unexpected results.

Navigating to Raster --> Miscellaneous --> Merge..., I set up the merge as follows:

Once the merge is complete, I see the following:

The first surprise is seeing the difference in the color map for the merged image versus the original components. Any idea how that is controlled?

And finally when I go to load the resulting merged image, I see the following:

There are visible hints of structure in the resulting image but clearly this isn't the anticipated result.

I'm running QGIS 3.6.1 on the Mac and am totally new to this system.

Answer 1

I just discovered the problem. Posting the answer here in case someone else has this issue. The output datatype needed to be set to Byte. Using ExifTool to look at the metadata for the original GeoTIFF files made it clear that each color channel was 8 bits.